function validate(){	
	var user_name_empty = "管理员用户名不能为空!";
	var user_pws_empty  = "管理员密码不能为空!";
	var user_name = document.getElementById('username').value;
	var user_pwd  = document.getElementById('password').value;
	if(user_name == "" || user_name == "null"){
		alert(user_name_empty) ;
		return false;
	}
	if(user_pwd == "" || user_pwd == "null"){
		alert(user_pws_empty) ;
		return false;
	}
}